1. Field of the Invention
The present invention relates to an image forming apparatus for forming an image on a sheet with feeding the sheet, such as a printer, a copier, a facsimile machine or a multifunction machine, and more particularly, to an image forming apparatus suitable for post-processing sheets such as stapling or punching sheets with using sheet post-processing information of edge and position identifying code.
2. Description of the Related Art
In either of Japanese Patent Application Publication No. 2002-241041 and No. 2003-266806, as shown in FIG. 34(A) for example, one edge of a sheet 1 is designated as a sheet binding margin 2, and an image on the back side of a sheet is rotated by 180° when a sheet feed direction is perpendicular to a sheet turning-over direction. In either of these publications, as shown in FIG. 35(A) for example, one edge of the sheet 1 is designated as the sheet binding margin 2, and sheet turning-over direction is determined on the basis of the sheet binding margin 2. On the other hand, since a sheet post-processing apparatus is configured to post-process sheets after aligning either a front end or a rear end of a stack of sheets in a sheet feed direction, a sheet feeding tray should be used wherein sheets are set so that either the front end or the rear end in the sheet feed direction is to be the sheet binding margin.
In a case of a sheet size, A4 size for example, where a longitudinal transfer (a transfer in which a short edge is perpendicular to the sheet feed direction) and a transverse transfer are selectable, the transverse transfer has a better printing efficiency.
(A) Problems Resulting from a Transfer Direction Determined on the Basis of a Sheet Binding Margin
However, in the prior art, as shown in FIG. 34(A), in a case where the sheet binding margin 2 is designated, although a stapling is executed on one end of the sheet binding margin 2 as shown in FIG. 34(B), the transverse transfer cannot be made, thereby causing the problem that the printing efficiency is deteriorated.
Conversely, when a transverse-transfer sheet is not set in a sheet feeding tray and a long edge of the sheet is designated as the sheet binding margin 2, there has been a problem that a printing is impossible.
In addition, for example, in a case where a sheet size is B4 and an image forming apparatus does not able to feed B4 sized sheet in transverse transfer, for a sheet binding margin 2 in FIG. 35(A), as shown in FIG. 35(B) for example, even in a case where one end of the sheet binding margin 2 is to be stapled, since the direction of transfer is determined by the sheet binding margin 2, there has been a problem that it is impossible to change to the longitudinal transfer as described above.
Furthermore, in a case shown in FIG. 34(B) for example, a stapling apparatus staples sheets on left end of the sheet binding margin, however, even if the longitudinal transfer is changed to the transverse transfer, the sheet post-processing is executed on the left end, thereby causing a problem that an unwanted finishing is made as shown in FIG. 34 (C).
In addition, in a case where both of the sheet staple-processing and punch-processing are to be executed in a single printing job, the respective data of each has no relation with each other, thereby causing the same problem when the sheet feed direction is changed.
Moreover, as shown in FIG. 3 of the Japanese Patent Application Publication No. 2002-241041, since a lot of binding position information on the sheet is used, many steps to sort the information should be executed, thereby causing a problem that a processing becomes complex.
(B) New Technical Problems Resulting from Solving the Above Problems
The present inventors have found that the problems can be solved by introducing the concept of a ‘post-processing-edge’ aside form the sheet binding margin. In this case, since the user's operability is greatly affected by how to process a setting error by a relationship with the post-processing-edge, the processing of the setting error becomes an important technical problem.
(C) Problems of a Sheet Punch-Processing in a Mixed Mode of Sheets with Different Sizes
Japanese Patent Application Publication No. 2002-232677 discloses a configuration in which sheet binding margin positions are aligned in a mixed mode of sheets with two different sizes in a single printing job.
For example, in a case of using A4 longitudinal and A3 transverse sheets, a first sheet to be printed is A4 and the long edge thereof is designated as the sheet binding margin, and for A3 sheets from the second sheet, the short edge of the A3 is designated as the sheet binding margin together with changing the information indicating the direction of an image by rotating by 90°, etc., relative to the image information (see FIG. 5 of the publication above). However, if the short edge of a large sized sheet and the long edge of a small sized sheet are different to each other, the mixed mode of the different sized sheets can not be applied thereto.
Meanwhile, since the sheet punching apparatus can form punch holes on one sheet after another, in the mixed mode of the different sized sheets, it is possible to overlap and discharge the sheets after forming the punch holes on both the A4 transverse-transfer sheet and the B5 longitudinal-transfer sheet as shown in FIG. 36.
That is, in the prior art, the capability of the sheet post-processing apparatus has not been sufficiently utilized.
Here, it is troublesome to separately set a sheet binding margin for each of the sheets with different sizes. In addition, if the punch holes are set on one sized sheet but the punch holes are inhibited from being set on the other sized sheet, setting the punch holes on the one sized sheet becomes useless, or since the punch holes are formed only on the one sized sheet, user's intention can not be achieved.
(D) Problems of Sheet Staple-Processing in a Double-Sided Printing Mode when Sheets with Different Sizes are Mixed
FIG. 37 shows a case where the double-sided printing is executed by using the sheets with different sizes in a single printing job and a stack of sheets is fixed with a staple.
Under the condition of binding the sheets with different sizes by arranging equilaterals among them, if a short edge binding is designated, as shown in FIG. 37(A), for the small size sheet the sheet binding margin 1 becomes parallel to the sheet feed direction. In contrast, for the large size sheet, as shown in FIG. 37 (D), the sheet binding margin 2 becomes perpendicular to the sheet feed direction. Thereby, each of the small size and large size sheets is turned-over by being rotated around the sheet binding margins 1 and 2 and the sheet turning-over directions of the sheets become thus different by 90° to each other so that a staple 3 should be driven in the common area of the sheet binding margins 1 and 2 as shown in FIG. 37 (G).
FIGS. 37(B) and (E) show directions of images printed on the back sides of sheets in (A) and (D), respectively. FIGS. 37(C) and (F) show, with dotted line, the images on the back sides of sheets in (A) and (D), respectively.
As above, since the situation occurs that the sheet turning-over directions are different by 90° in the small size and the large size sheets, it can not meet user's demand that the sheet turning-over directions should be identical regardless of sizes.
In addition, as disclosed in Japanese Patent Application Publication No. 2002-232677 in the case of making the sheet binding margin by arranging equilaterals among the sheets with different sizes, as shown in FIG. 22 (C), the stack of sheets should be rotated by 90° by replacing the small size and the large size sheets. Therefore, it can not meet user's demand that the sheet turning-over directions should be identical without rotating the stack of sheets.
Meanwhile, since the sheet post-processing apparatus mounted on the image forming apparatus executes the sheet post-processing on either of the front end or the rear end of the sheet feeding direction of a sheet, for example, the sheet binding margin 1 in FIG. 37 should be the front end of the sheet feed direction, and in the case of FIG. 37, since the length of edge of a sheet can not be arranged as the front end of the sheet feeding direction, the sheet post-processing can not be executed.
(E) Problems in the Relation Between Image Forming Direction and Set Condition for the Sheet Feeding Tray of a Special Sheet where a Pre-Processing is Executed
There are cases to form an image on a special sheet where a pre-processing is executed so that the direction of the image to be formed should be set, such as a pre-punched sheet where holes have previously been perforated and a pre-printed sheet (including a letter head sheet) where an image such as a rule or a items listing blank, etc., has previously been formed.
In a single printing job for such a special sheet, in the case where a double-sided printing and a single-sided printing are mixed, Japanese Patent Application Publication No. 2005-174711 filed by the present applicant executes processes as described below. That is, in the case where the double-sided printing is executed by the image forming apparatus, it first forms an image on the back side and then forms a front side image by reversing the special sheet and discharges the sheet to a face down sheet discharge tray. In the case of the single-sided printing, it inserts blank sheet image information on a back side dummy page and executes the double-sided printing but at the same time, the back side should not be counted.
Thereby, for example, in the case where the images on the first, second, fourth and fifth pages are formed by the double-sided printing, and the image on the third page is formed by the single-sided printing, the images are formed in a desired order as shown in FIG. 38, thereby solving the problem of the apparatus that the sheet must pass through a printer engine three times to perform the double-sided printing described in Japanese Patent Application Publication No. 2003-050482.
Here, if the special sheet is stapling processed with a finisher, for the reason associated with a mechanism, the special sheet should be usually fed so that a sheet staple-processing edge should be the front end of the sheet feed direction. Meanwhile, there is a case where front and back sides of the special sheet are reversed to be set in the sheet feeding tray. For example, since the directions to be turned over become opposite depending on a vertical writing and horizontal writing, there is a need to set the front and back sides reversed.
FIG. 39(A) schematically shows a duplex pre-printed sheet as the special sheet. As shown in the drawing, in the case where the direction of the image to be formed (the direction of the pre-printed image) is perpendicular to the sheet feed direction, if the front and back sides of the special sheet are reversed so that the sheet staple-processing edge should be the front end of the sheet feed direction, the image is in a state whereby it is rotated by 180° as shown in FIG. 39(B) and the image forming apparatus needs to make the image which is formed to rotate by 180°.
The conventional image forming apparatus, regardless of a rotating reason, comprises a (general) simple setting function to rotate the image by 180°, however, it must have been considered to be set in order to certainly and correctly rotate the image by 180° depending on the set condition of the special sheet by a user.